Patches and Bonine both work well. Sea sickness is partly caused by you body feeling motion, but your eyes/mind not seeing the motion (if all of your surroundings moving in concert, it looks like there is no motion -- ala the motion of the earth). Being able to see the horizon helps some, as their eye/mind can not also detect the motion.
As Donna said, the motion is very faint, especially in the W. Carib. Just carry some Bonine or a patch with you in case you need it. I think they have them on board too, but they will be much more expensive.